A dazzling new image from NASA’s Hubble Space Telescope resembles a red, white, and blue sparkler lighting up the night sky. Released in honor of the United States’ 250th anniversary, the striking view celebrates the nation’s long tradition of exploration while highlighting one of the oldest star clusters in the Milky Way.
One of the Milky Way’s Oldest Star Clusters
The image features NGC 6426, a globular cluster located in the outer halo of the Milky Way. Globular clusters are tightly packed, nearly spherical collections of stars held together by gravity. Astronomers have identified about 150 of these ancient clusters within our galaxy.
Because the stars in a globular cluster typically form from the same collapsing cloud of gas, they are generally close in age. NGC 6426 is estimated to be about 13 billion years old, making it one of the oldest known globular clusters in the Milky Way. At only slightly younger than the universe itself, which is approximately 13.7 billion years old, it provides a remarkable glimpse into the earliest stages of cosmic history.
What the Colors Reveal About the Stars
The vibrant colors in the Hubble image are based on the wavelengths of light captured through different telescope filters using standard image processing methods.
Blue represents shorter wavelengths of visible light, while red shows longer visible wavelengths along with some near-infrared light. Because a star’s color is closely tied to its temperature, the blue stars are hotter, while the red stars are cooler.
Clues to the Early Universe
The stars in NGC 6426 have what astronomers call low metallicity, meaning they contain relatively small amounts of elements heavier than hydrogen and helium. Those conditions closely resemble those found in the young universe, when hydrogen and helium dominated, and heavier elements had only begun forming inside massive stars through nuclear fusion.
Researchers have also identified evidence that NGC 6426 contains two chemically distinct groups of stars. This suggests that a second generation of stars formed after the cluster’s earliest massive stars exploded as supernovae, enriching the surrounding gas with newly created heavy elements.
Those powerful stellar explosions scattered elements heavier than hydrogen and helium throughout the cluster, providing the raw materials needed to form future generations of stars and, eventually, planets.
Hubble Continues Exploring the Galaxy’s History
Hubble captured this image as part of a larger project examining globular clusters throughout the Milky Way’s halo. By studying these ancient stellar systems, astronomers hope to better determine their ages and gain new insights into how our galaxy formed and evolved.
Over more than three decades in orbit, the Hubble Space Telescope has transformed scientists’ understanding of the universe. Its discoveries continue to be expanded by other NASA observatories, including the James Webb Space Telescope, while the upcoming Nancy Grace Roman Space Telescope, scheduled to launch in late summer, is expected to build on that legacy even further.
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